(a) Field of the Invention
The present invention relates to a catalytic cracking catalyst useful for catalytic cracking heavy oils, methods of production thereof, and a method of catalytic cracking of heavy oil using the catalytic cracking catalyst.
(b) Description of the Related Art
In these days of increasingly heavier heavy oils and increasing demands for white oils (gasoline, kerosene and diesel fuel) rather than heavy oils, catalytic cracking of heavy oils has becoming very important. This has caused a demand for improved catalytic cracking catalysts which increase the yields of gasoline and LCO (light oil fractions).
To crack tower bottoms of heavy oils, such as desulfurized heavy oils, large pores of catalytic cracking catalysts should be increased to allow easy penetration of the tower bottoms into the catalysts to cause initial rough cracking. The products of the rough cracking are then further cracked by zeolites contained in the catalysts, to form light distillates including gasoline and LCO.
Without large pores, catalysts cannot allow raw materials of large molecules to penetrate therein and cannot work effectively, so that the yields of products of low economical value, such as coke and heavy oils, are increased.
Therefore, it is necessary to crack the tower bottoms of heavy oils in pores of different sizes in steps, first in pores of 2,000 to 18,000 .ANG. and then in pores of 200 to 2,000 .ANG..
Some of the literature refers to the sizes of pores of catalytic cracking catalysts. Japanese Patent Application Unexamined Publication No. 6-25675 (1994) discloses meso-porous cracking catalysts, which, however, have a pore distribution with a peak around 150 to 350 .ANG., and cannot crack tower bottoms of heavy oils to give sufficiently high yields of gasoline and LCO. Japanese Patent Application Unexamined Publication No. 2-298351 (1990) refers to pore distribution of catalytic cracking catalysts, but does not clarify the amount of large pores and the forms of pores. Further, it does not disclose the production of catalysts using silica alumina or alumina which has a sharp pore diameter peak. Japanese Patent Application Unexamined Publication No. 55-109446 (1980) discloses forming pores of about 100 to 275 .ANG. in diameter by decomposing organic polymers which are mixed into the raw materials of catalysts. Such pores, however, cannot crack the tower bottoms of heavy oils sufficiently to increase gasoline and LCO yields.